U.S. patent number 5,105,620 [Application Number 07/648,295] was granted by the patent office on 1992-04-21 for secondary air supply system for supercharged engine.
This patent grant is currently assigned to Nissan Motor Co., Ltd.. Invention is credited to Motohiro Matsumura.
United States Patent |
5,105,620 |
Matsumura |
April 21, 1992 |
Secondary air supply system for supercharged engine
Abstract
A secondary air supply system for a supercharged engine includes
a control valve which controls a diaphragm-operated valve. The
control valve with solenoid is electrically controlled according to
various engine operating conditions. The diaphragm-operated valve
tightly closes the secondary air supply passage to prevent exhaust
gas from flowing into the intake passage through the secondary air
supply passage under a high engine load and high engine speed
condition. The diaphragm-operated valve opens the secondary air
supply passage to allow air to be supplied into the exhaust gas
under a low engine load and low engine speed condition.
Inventors: |
Matsumura; Motohiro (Kanagawa,
JP) |
Assignee: |
Nissan Motor Co., Ltd.
(Yokohama, JP)
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Family
ID: |
12009901 |
Appl.
No.: |
07/648,295 |
Filed: |
January 30, 1991 |
Foreign Application Priority Data
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Feb 28, 1990 [JP] |
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2-19818[U] |
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Current U.S.
Class: |
60/290; 60/293;
60/280 |
Current CPC
Class: |
F02B
37/168 (20130101); F01N 9/00 (20130101); F02B
37/16 (20130101); F01N 3/22 (20130101); F01N
3/227 (20130101); F02B 37/164 (20130101); Y02T
10/22 (20130101); Y02T 10/144 (20130101); Y02T
10/47 (20130101); Y02T 10/40 (20130101); Y02T
10/12 (20130101) |
Current International
Class: |
F02B
37/12 (20060101); F02B 37/16 (20060101); F01N
9/00 (20060101); F01N 3/22 (20060101); F01N
003/22 (); F02B 037/00 () |
Field of
Search: |
;60/293,290,280 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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53-76217 |
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Jul 1978 |
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JP |
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93919 |
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Jul 1980 |
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JP |
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58-172415 |
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Oct 1983 |
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JP |
|
Primary Examiner: Hart; Douglas
Attorney, Agent or Firm: Foley & Lardner
Claims
What is claimed is:
1. A secondary air supply system for an internal combustion engine
with a supercharger, comprising:
means for defining a secondary air supply passage which
communicates with intake and exhaust passages of the engine;
a reed valve disposed in said secondary air supply passage, said
reed valve being operated so that air in the intake passage is
supplied into exhaust gas in the exhaust passage;
a diaphragm-operated valve disposed in said secondary air supply
passage and having a pressure chamber defined by a diaphragm, said
diaphragm-operated valve opening said secondary air supply passage
in a first state when the pressure chamber is supplied with
negative pressure from the intake passage, closing said secondary
air supply passage in a second state when the pressure chamber is
supplied with positive pressure from the intake passage, said
positive pressure being developed by the supercharger, and closing
said secondary air supply passage in a third state when the
pressure chamber is supplied with atmospheric pressure;
valve means operatively connected to said diaphragm-operated valve
whereby in said first state said pressure chamber is supplied with
the negative pressure, in said second state said pressure chamber
is supplied with the positive pressure, and in said third state
said pressure chamber is supplied with atmospheric pressure;
and
means for controlling said valve means to put said valve means into
said first state in a first engine operating condition, said second
state in a second engine operating condition in which an engine
load and an engine speed are higher than those in said first
condition, and said third state in a third engine operating
condition in which said engine load and said engine speed are other
than those in said first and second engine operating
conditions.
2. A secondary air supply system as claimed in claim 1, wherein
said first engine operating condition is a low engine load and low
engine speed condition, and said second engine operating condition
is a high engine load and high engine speed condition.
3. A secondary air supply system as claimed in claim 2, wherein
said low engine load and low engine speed condition is an idling
condition.
4. A second air supply system as claimed in claim 1, wherein said
diaphragm-operated valve includes a valve seat defining an opening
forming part of the secondary air supply passage, a valve member
fixedly connected to said diaphragm and being seatable on said
valve seat to close the opening, said valve member being adapted to
separate from said valve seat when said pressure chamber is
supplied with the negative pressure and to be forced on said valve
seat when said pressure chamber is supplied with the positive
pressure, and a spring for biasing said valve member on said valve
seat so that said valve member is seated on said valve seat when
said pressure chamber is supplied with atmospheric pressure.
5. A secondary air supply system as claimed in claim 1, wherein
said controlling means includes means for detecting said engine
load and said engine speed and generating first, second and third
electrical signals respectively corresponding to said first, second
and third engine operating conditions, and a control unit
electrically connected to said detecting means and adapted to put
said valve means into said first, second and third states
respectively in response to said first, second and third electrical
signals.
6. A secondary air supply system as claimed in claim 1, further
comprising a three-way catalytic converter disposed in the exhaust
passage downstream of a portion communicated with said secondary
air supply passage.
7. A secondary air supply system as claimed in claim 1, wherein
said pressure chamber is communicated with a part of the intake
passage located downstream of a throttle valve of the engine.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to improvements in a secondary air
supply system which is used in a supercharged engine, and more
particularly to such a secondary air supply system which improves
engine performance in a high engine load and high engine speed
condition.
2. Description of the Prior Art
It is well known to use a three-way catalytic converter (a device
which is capable of simultaneously reducing the concentrations of
CO, HC and NO.sub.x in the exhaust gases) in the exhaust system of
automotive engines. Such a conventional system, however, cannot
efficiently convert CO and NO.sub.x when an enriched air/fuel
mixture is supplied to the engine under an idling condition. To
efficiently convert the exhaust gases under the idling condition,
it has been proposed that the exhaust system be provided with a
secondary air supply arrangement wherein secondary air is supplied
into the exhaust gases under an idling condition. Such an
arrangement is disclosed, for example, in Japanese Patent
Provisional Publication Nos. 53-76217 and 58-172415. The secondary
air supply arrangement includes a diaphragm valve which opens a
secondary air supply passage so that secondary air is supplied into
the exhaust gases under an idling condition. The arrangement
further includes a reed valve which operates to guide the secondary
air into the exhaust gases under the pulsation of the exhaust
gas.
However, when this conventional arrangement is used in a
supercharged engine, a problem arises because the exhaust gas flows
into the intake passage through the secondary air supply passage
under a high engine load and high engine speed condition. This
occurs sealing performance of the reed valve being not very good,
the arrangement cannot prevent the exhaust gas from leaking at the
reed valve. The diaphragm-operated valve is opened by communication
between the pressure chamber of the diaphragm-operated valve and
negative pressure in the intake passage, thereby guiding secondary
air into the exhaust gas. The diaphragm-operated valve is closed by
communication between the pressure chamber and the atmosphere under
other than the high load and speed condition. Therefore, under a
high pressure condition of the exhaust gas such as a high engine
load and high engine speed condition, the exhaust gas leaking from
the reed valve pushes and opens the diaphragm-operated valve.
Furthermore, the exhaust gas flows into the engine through the air
cleaner, thereby degrading the engine performance under a high
engine load and high engine speed condition.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a secondary air
supply system to improve the performance of a supercharged engine
under a high engine load and high speed revolution condition, while
also providing an improved secondary air supply system whereby
secondary air is led into the exhaust gas under a predetermined low
engine load and low speed revolution condition.
A secondary air supply system for an internal combustion engine
with a supercharger of, according to the present invention,
comprises a secondary air supply passage which communicates with
intake and exhaust passages of the engine. A reed valve is disposed
in said secondary air supply passage and operated so that air in
the intake passage is supplied into the exhaust gas in the exhaust
passage. A diaphragm-operated valve is disposed in the secondary
air supply passage and has a pressure chamber defined by a
diaphragm. The diaphragm-operated valve opens the secondary air
supply passage in a first state when the pressure chamber is
supplied with negative pressure from the intake passage. In a
second state the secondary air supply passage is closed and exhaust
gas is prevented from flowing from the exhaust passage to the
intake passage through the secondary air supply passage. The second
state occurs when the pressure chamber is supplied with positive
pressure developed by the supercharger in the intake passage. A
third state also closes the secondary air supply passage when the
pressure chamber is supplied with atmospheric pressure. A valve
means is operatingly connected to the diaphragm-operated valve and
in a first state allows the pressure chamber to be supplied with
negative pressure, in a second state allows the pressure chamber to
be supplied with positive pressure, and in a third state allows the
pressure chamber to be supplied with atmospheric pressure. A valve
means controlling means puts the valve means into one of the first
state in a first engine operating condition, the second state in a
second engine operating condition in which engine load and engine
speed are higher than those in the first condition, and the third
state in a third engine operating condition in which the engine
load and the engine speed are other than those in the first and
second engine operating conditions.
With this arrangement, the diaphragm-operated valve tightly closes
the secondary air passage under a high engine load and high engine
speed condition so that the exhaust gas is prevented from flowing
into the engine through the intake passage. Therefore, the
supercharged engine has improved power performance under a high
engine load and high engine speed condition, while secondary air is
supplied into exhaust gas under a predetermined low engine load and
low engine speed condition such as an idling condition.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a schematic view of an engine system including a
secondary air supply system according to the present invention;
FIG. 2 is a cross-sectional view of a valve unit of the secondary
air supply system of FIG. 1;
FIG. 3 is a flowchart showing a program of the system according to
the present invention; and
FIG. 4 is a graph showing an operating condition of a control valve
of the secondary air supply system in accordance with the engine
condition.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to FIGS. 1 to 4, an embodiment of a secondary air
supply system according to the present invention is illustrated by
the reference character S. The secondary air supply system S is, in
this embodiment, installed in an internal combustion engine system
E of an automotive vehicle (not shown). The internal combustion
engine system E includes an internal combustion engine 1 equipped
with a turbocharger 4 which has an intake compressor 6 and an
exhaust turbine 9. A combustion chamber (or combustion chambers) 1a
of the internal combustion engine 1 is communicable with an intake
passage 2 and an exhaust passage 3 as usual.
An air cleaner 5 is disposed in the intake passage 2 at a portion
near its upstream end. The intake compressor 6 is disposed in the
intake passage 2 downstream of the air cleaner 5. An inter cooler 7
for cooling compressed intake air is disposed in the intake passage
2 downstream of the intake compressor 6. A throttle valve 8 and a
fuel injection valve (not shown) are disposed in the intake passage
2 downstream of the inter cooler 7. An intake manifold 1b is
disposed in the intake passage 2 to be connected with the
combustion chamber 1a. In the exhaust passage 3, the exhaust
turbine 9 is disposed downstream of the engine combustion chamber
1a. An oxygen sensor 10 is disposed downstream of the exhaust
turbine 9. A three-way catalytic converter 25 is disposed
downstream of the oxygen sensor 10.
A secondary air supply passage 12 has an upstream end 12a and a
downstream end 12b. The upstream end 12a is communicated with the
intake passage 2 upstream of the air cleaner 5. The downstream end
12b is communicated with the exhaust passage 3 upstream of the
three-way catalytic converter 25.
A diaphragm-operated valve 14 is disposed in the secondary air
passage 12 to close the secondary air supply passage 12. As shown
in FIG. 2, the diaphragm-operated valve 14 includes a diaphragm 16
which defines a pressure chamber 15. A valve member 17 is connected
to the diaphragm 16 and disposed to close an opening (no numeral)
defined by a valve seat 12c, whereby the opening forms part of the
secondary air passage 12. A spring 18 is disposed in the pressure
chamber 15 to bias the diaphragm 16.
The secondary air supply passage 12 has a reed valve 13 which opens
and closes an opening (no numeral) defined by a valve seat 12d,
whereby the opening forms part of the secondary air supply passage
12. The opening and closing action of the reed valve 13 is caused
by the pulsation of exhaust gas in the exhaust passage 3 so that
secondary air in the intake passage 2 is supplied into the exhaust
gases in the exhaust passage 3. The reed valve 13 and the
diaphragm-operated valve 14 are assembled to form a valve unit U as
shown in FIG. 2 so that the reed valve 13 is located downstream of
the diaphragm-operated valve 14. A control passage 14a communicates
with the pressure chamber 15 and the intake passage 2 downstream of
the throttle valve 8. When negative pressure (vacuum) is supplied
to the pressure chamber 15 through the control passage 14a, the
valve member 17 is lifted up and the secondary air supply passage
12 is opened. When positive pressure or atmospheric pressure is
supplied to the pressure chamber 15, the valve member 17 closes the
secondary air supply passage 12.
A control valve 19 is arranged to be opened when a solenoid thereof
is energized and to be closed when the solenoid is de-energized.
The control valve 19 is installed for the control passage 14a so
that the pressure chamber 15 is communicated with atmosphere when
the control valve 19 is opened. Therefore, when the control valve
19 is closed, the intake air pressure in the intake passage 2 is
supplied to the pressure chamber 15. When the control valve 19 is
opened, atmospheric pressure is supplied to the pressure chamber
15.
An air flow sensor 20 is disposed in the intake passage 2
downstream of the air cleaner 5 in order to detect the intake air
flow rate of the engine 1. Furthermore, the engine 1 is provided
with a throttle-position sensor 21 for detecting an opening angle
or throttle position of the throttle valve 8. A water temperature
sensor 22 is installed on the engine 1 to detect the temperature of
the cooling water in the engine 1. An engine speed sensor 23 is
installed on the engine 1 to detect the engine speed of the engine
1. A control unit 24 for controlling the control valve 19 is
electrically connected to the control valve 19, the air flow sensor
20, the throttle sensor 21, the water temperature sensor 22 and the
engine speed sensor 23. Therefore, the control unit 24 operates in
response to the signals detected by the sensors 20, 21, 22 and 23
so that the exhaust gas condition is controlled adequately. Thus,
when the engine 1 operates under a predetermined low engine load
and low engine speed condition or a high engine load and high
engine speed condition, the control valve 19 is closed so that the
pressure chamber 15 communicates with the intake passage 2
downstream of the throttle valve 8. The engine load is represented
by an equation (K.times.Q/Rev.) where K is a predetermined value, Q
is the air flow rate and Rev. is the engine speed. When the engine
1 operates under another condition such as a partial engine load
condition, the control valve 19 is opened so that the pressure,
chamber 15 communicates with the atmosphere. The operation of the
control valve 19 corresponding to the engine operating condition is
shown in the graph of FIG. 4. In the graph, a zone A.sub.1
represents the low engine load and low engine speed condition in
which the control valve 19 is closed. A zone A.sub.2 represents the
high engine load and high engine speed condition in which the
control valve 19 is closed. Zones B.sub.1 and B.sub.2 represent the
other engine operating condition in which the control valve is
opened. A line a represents an engine operating condition under
which a pressure in the intake manifold 1b is held at 0 mmHg.
Under a normal operating condition of the engine 1, the control
unit 24 controls fuel injection amounts in response to the signals
from the sensors 20, 21, 22 and 23 so that the air/fuel mixture for
the engine 1 is controlled in a predetermined (stoichiometric)
air/fuel ratio. Under an idling condition or the like of the engine
1, the amount of injected fuel is controlled so that the air/fuel
ratio is enriched over the stoichiometric air/fuel ratio.
The manner of operation of the thus arranged secondary air supply
system S will be discussed hereinafter with reference to the
flowchart of FIG. 3.
When it is judged in a step S101 that the engine 1 is under an
idling condition, the flow goes to a step S102. When it is judged
in a step S102 that a temperature T.sub.w of the cooling water in
the engine 1 is higher than a predetermined level T.sub.wa, the
flow goes to a step S103. When it is judged in the step S103 that
the engine 1 is under an air/fuel ratio condition enriched over the
stoichiometric ratio, the flow goes to a step S104. In the step
S104, the control valve 19 is closed.
When it is judged in the step S101 that the engine 1 is not under
the idling condition, the flow goes to a step S105. When it is
judged in the step S105 that an engine speed N.sub.r is higher than
a predetermined value N.sub.r1, the flow goes to a step S106. When
it is judged in the step S106 that the engine load T.sub.p
(K.times.Q/Rev.) is higher than a predetermined value T.sub.p1, the
flow goes to a step S107. In the step S107, the control valve 19 is
closed.
Further, when it is judged in the step S102 that the cooling water
temperature T.sub.w is not higher than the level T.sub.wa, the flow
goes to a step S108. In the step S108, the control valve 19 is
opened. Similarly, when it is judged in the step S103 that the
air/fuel ratio is not enriched over the stoichiometric air/fuel
ratio, the flow goes to the step S108. When it is judged in the
step S105 that the engine speed N.sub.r is not higher than the
value N.sub.r1, the flow goes to the step S108. When it is judged
in the step S106 that the engine load T.sub.p is not higher than
the value T.sub.p1, the flow goes to the step S108.
With the thus arranged system, when the control valve 19 is closed
under the low engine load and low engine speed condition within the
zone A.sub.1, the pressure chamber 15 is communicates with the
intake passage 2 downstream of the throttle valve 8 so that the
diaphragm-operated valve 14 opens the secondary air supply passage
12.
When the control valve 19 is opened under a partial-load condition
within the zone B, the pressure chamber 15 is communicated with
atmosphere so that the diaphragm-operated valve 14 closes the
secondary air supply passage 12. Since exhaust gas pressure in the
exhaust passage 3 is not so high under the partial engine load or
the like condition of the engine 1, the exhaust gas does not flow
into the secondary passage 12.
When the control valve 19 is closed under a high engine load and
high engine speed condition within the zone A.sub.2, the pressure
chamber 15 communicates with the intake passage 2 so that a
positive pressure caused by the turbocharger 4 communicates with
the pressure chamber 15. Accordingly, the diaphragm-operated valve
14 is operated so that the valve member 17 tightly closes the
secondary air supply passage 12, even though high exhaust pressure
is applied to the valve member 17 through the reed valve 13.
Therefore, the exhaust gas cannot flow into the intake passage 2,
thereby maintaining a high power performance of the engine 1.
When the pressure chamber 15 of the diaphragm valve 14 communicates
with the atmosphere under a partial engine load condition of the
engine 1, the secondary air supply passage 12 is closed by the
valve member 17. However, if the engine 1 is operated so that the
intake pressure is under a negative pressure condition and not
under the low engine load and low engine speed condition, for
example, under a condition within the zone B.sub.1 in FIG. 4, the
pressure chamber 15 may be communicated with the intake passage
2.
* * * * *